Users may tend to dial certain telephone numbers unintentionally and then disconnect after a ring or two upon realizing their error. For example, certain numbers, such as 9, may be designated for some generic purpose, such as operator assistance or a helpline. But another prefix number, such as 8, may be used for external calls, for example. Rather than dialing the prefix number for an external call, a user may mistakenly dial 9, leading to the operator, and immediately disconnect upon realizing the error. This may lead to inconvenience for both the user and the unintentionally called party.